🧪 test: add HTTP test files for agents and sessions APIs

- Add agents.http with comprehensive API endpoint tests
- Add sessions.http for session management testing
- Include authentication setup and request examples
- Support testing of CRUD operations for both agents and sessions

These files enable easy API testing and validation during development.

tests/apis/agents/agents.http

@@ -0,0 +1,55 @@
+@host=http://localhost:23333
+@token=cs-sk-af798ed4-7cf5-4fd7-ae4b-df203b164194
+
+### List Agents
+GET {{host}}/v1/agents
+Authorization: Bearer {{token}}
+
+
+### Create Agent
+POST {{host}}/v1/agents
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+{
+  "name": "Claude Code",
+  "type": "claude-code",
+  "model": "anthropic:claude-sonnet-4",
+  "description": "An AI assistant specialized in code review and debugging",
+  "avatar": "https://example.com/avatar.png",
+  "instructions": "You are a helpful coding assistant. Focus on writing clean, maintainable code and providing constructive feedback.",
+  "accessible_paths": [
+    "/tmp/workspace"
+  ],
+  "permission_mode": "acceptEdits",
+  "max_steps": 10
+}
+
+### Get Agent Details
+GET {{host}}/v1/agents/agent_1757663884173_4tyeh3vqq
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+### Delete Agent
+DELETE {{host}}/v1/agents/agent_1757663884173
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+### Update Agent
+PATCH {{host}}/v1/agents/agent_1757663884173
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+{
+  "name": "Claude Code",
+  "model": "anthropic:claude-sonnet-4",
+  "description": "An AI assistant specialized in code review and debugging",
+  "avatar": "https://example.com/avatar.png",
+  "instructions": "You are a helpful coding assistant. Focus on writing clean, maintainable code and providing constructive feedback.",
+  "accessible_paths": [
+    "/tmp/workspace"
+  ],
+  "permission_mode": "acceptEdits",
+  "max_steps": 10
+}
+

tests/apis/agents/sessions.http

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+
+@host=http://localhost:23333
+@token=cs-sk-af798ed4-7cf5-4fd7-ae4b-df203b164194
+@agent_id=agent_1757663884173_4tyeh3vqq
+
+### List Sessions
+GET {{host}}/v1/agents/{{agent_id}}/sessions
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+
+### Create Session
+POST {{host}}/v1/agents/{{agent_id}}/sessions
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+{
+  "name": "Code Review Session",
+  "user_goal": "Review the newly implemented feature for bugs and improvements"
+}
+
+### Get Session Details
+GET {{host}}/v1/agents/{{agent_id}}/sessions/session_1757815281790_q4yxgdk74
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+### Delete Session
+DELETE {{host}}/v1/agents/{{agent_id}}/sessions/session_1757815245456_tfs6oogl0
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+### Update Session
+PUT {{host}}/v1/agents/{{agent_id}}/sessions/session_1757815281790_q4yxgdk74
+Authorization: Bearer {{token}}
+Content-Type: application/json
+
+{
+  "name": "Code Review Session 1",
+  "user_goal": "Review the newly implemented feature for bugs and improvements"
+}